This invention relates generally to jaw-type surgical instruments and, in particular, to a jaw-type surgical instrument wherein the opposed jaws move substantially parallel over a significant part of their operating range and/or wherein one of the jaws includes a cartridge having a knife assembly that is detachable from its operating mechanism.
A wide variety of surgical procedures used today involve surgical instrumentation having jaw structure such as grippers, graspers, dissectors, clamps, cutting elements and/or stapling elements. In each of these types of jaw structure, selected tissue is captured by the jaws for manipulation. One type of jaw structure currently used captures tissue by a pivotal action of the jaw structure wherein the jaws close progressively from a pivot point outward to the end of the jaw structure. See, for example, U.S. Pat. No. 5,040,715 to Green et al. This pivotal action, however, causes the captured tissue to be pushed away from the jaw pivot point upon approximation, possibly resulting in uneven cutting, unintentional tissue trauma, and/or inaccurate tissue measurement or joining. This type of jaw structure is also disadvantageous in endoscopic or laparoscopic procedures wherein the surgical instrument is inserted into the body through a cannula or trocar because the jaws must necessarily protrude a significant distance beyond the end of the trocar to open fully. This decreases the xe2x80x9cmaneuver roomxe2x80x9d available to a surgeon for manipulating the device within a body cavity.
A more accurate and a traumatic way of approximating surgical jaw structure is by parallel approximation. This approach has been described in European Patent Application No. 92104388.1, filed Mar. 13, 1992, wherein various camming structures are described for effecting substantially parallel movement of first and second surgical jaws. In one embodiment, a camming plate with diagonal camming slots is slidably mounted within a tubular frame. The camming plate is connected to a moveable jaw such that movement of the camming plate causes the moveable jaw to move into parallel approximation with a stationary jaw. In another embodiment, an axially slidable camming collar engages a camming surface on the moveable jaw to actuate the opening and closing of the jaws. Sliding the collar forward closes the jaws, whereas pulling the collar backward opens the jaws. This design, however, creates a very high frictional component to the overall opening and closing forces, affecting the overall ease of operation of the device. Additionally, in all of the embodiments described, the jaws are prevented from moving axially, which, as will be discussed below, precludes the user from enjoying many other advantages.
The above devices also describe jaw structures that employ a staple cartridge. Typically, the staple cartridge is provided with an axially extending slit through which a knife passes to cut the captured tissue at the time of stapling. An axially moveable actuating mechanism (e.g., a pusher rod) is used to push the knife through the cartridge. The location and structure of the knife actuating mechanism is well known for jaws having purely pivotal movement, but such is not the case for jaws that are capable of substantially parallel approximation. In this latter situation, especially in connection with endoscopic or laparoscopic procedures where accessibility is extremely limited, inclusion of the knife actuating mechanism can result in a reduction in the maximum distance the jaws can open and/or result in further penetration of the jaws beyond the end of the cannula into the body cavity to accommodate the knife actuating mechanism.
It is also desirable to have a fresh knife available after each transection. In presently available apparatus, however, the knife has been an integral part of the combined pusher rod/cartridge assembly. This design requires the pusher rod mechanism to be discarded after each use, causing waste, and requires that the overall length of the cartridge assembly be increased in size to account for the entire extended length of the pusher rod mechanism.
Another disadvantage of the above-described devices is that jaw closing is typically accomplished by actuating an axially movable rod operably connected to the jaws. Pushing on the actuating rod closes the jaws and pulling on it opens them. Using compression force on the actuating rod, however, to close the jaws around the captured tissue can result in buckling. This could have serious consequences if buckling occurred during a particularly sensitive part of the surgical procedure.
In view of the above, it should be appreciated that there is still a need for a jaw-type surgical instrument wherein the jaws are held substantially parallel over a significant part of their operating range, yet open widely with minimal extension of the jaws beyond the end of the cannula into the body cavity during the operating procedure. There is also a need for a device wherein the jaws are axially moveable to effect approximation and wherein the mechanism for closing the jaws around the captured tissue is without risk of instrument failure due to buckling of the push rod. Such a device would also preferably include an easily replaceable knife without significantly affecting the operation of the jaws or requiring frequent replacement of the knife actuating mechanism. The present invention satisfies these needs.
The present invention is embodied in a surgical instrument having an articulated jaw structure, wherein a pair of jaws are held substantially parallel over a significant part of their operating range, yet are capable of being held widely open with minimal extension of the jaws beyond the end of a mounting cannula or frame during an operating procedure. One or both jaws are adapted to be axially moveable relative to the frame. The surgical instrument also includes a jaw operating mechanism that is not subject to buckling during jaw approximation. The present invention is particularly adapted for use in surgical stapling instrumentation and permits the use of a staple cartridge/knife assembly combination that is relatively short in length and easily replaceable.
In one embodiment of the invention, the surgical instrument with articulated jaw structure includes a tubular frame and an actuating mechanism moveable inside the tubular frame. The actuating mechanism has a cam that engages corresponding camming surfaces on first and second jaws. Each of the jaws has a proximal portion defining the camming surface and a distal portion. The proximal portions of the jaws are pivotally mounted to each other. The distal portions of the jaws are configured to capture tissue between them. The cam and camming surfaces are configured such that upon movement of the cam between a first position and a second position, the jaws will pivot relative to each other between an open position and an intermediate position, respectively. One of the jaws also includes a cam stop that further engages the cam when the cam is in the second position such that upon further movement of the actuating mechanism between the second position and a third position, the jaws will retract axially into the tubular frame. One of the jaws further includes a ramp that engages a distal end of the tubular frame upon axial retraction of the jaws. The ramp is configured such that the jaws move in a substantially parallel relation between the intermediate position and an approximated position upon movement of the cam between the second position and the third position, respectively.
A feature of this embodiment of the invention is that the jaw motion may be broken down into two components, a primarily pivoting motion of the jaws during initial jaw closing, which does not consume significant axial length between the distal portions of the jaws and the tubular frame and a substantially parallel approximating motion of the jaws that does consume axial length as the jaws are retracted into the tubular frame. Through this construction, axial stroke is substantially limited to the latter high force segment of the jaw closing cycle (i.e., the compression of tissue by the approximating jaws). In turn, a shorter axial stroke means less extension of the jaws beyond the end of the tubular frame and less protrusion into the body cavity, increasing the xe2x80x9cmaneuver roomxe2x80x9d of the surgeon manipulating the instrument.
Another feature of the present invention is that the jaw mechanism may be operated by an actuating rod that closes the jaws upon pulling the rod and opens the jaws upon pushing the rod. Using tensile force to close the jaws reduces the likelihood that the actuating rod will buckle. Buckling can only occur during compressive loading, which occurs during jaw opening. Since the jaw opening force is always lower than the jaw closing force, the maximum buckling force is lower than it would be if the situation were reversed.
In a second embodiment of the present invention, the surgical instrument with articulated jaw structure includes a frame, a fixed jaw mounted to the frame at its proximal end and a moveable jaw. The moveable jaw is connected to the fixed jaw to permit movement between an open position wherein the distal ends of the jaws are spaced apart from each other and the moveable jaw is extended distally relative to the fixed jaw, and an approximated position wherein the distal ends of the jaws are closer together and the moveable jaw is substantially unextended relative to the fixed jaw. An actuating mechanism is provided for moving the jaws between the open and approximated positions.
A particular feature of the second embodiment of the invention is that the moveable jaw juts out from the fixed jaw when the jaws are open. As the jaws close, the moveable jaw moves back along the fixed jaw, pulling tissue back toward the proximal end of the jaws. This inhibits tissue from extruding out of the gap between the jaws, which is opposite to the undesirable result caused by the prior art single pivot jaws wherein the tissue is pushed out of the jaws during closing.
The present invention is also embodied in a surgical instrument having articulated jaw structure and a detachable knife. By including a mechanism for engaging and disengaging a knife, the jaws can be held substantially parallel over a significant part of their operating range, yet still open widely with minimal extension of the jaws beyond the end of their mounting cannula or frame. In addition, because the knife is detachable, the knife may be replaced often without requiring replacement of its actuating mechanism.
The surgical instrument with articulated jaw structure and detachable knife of the present invention includes a first jaw and a second jaw, one of the jaws having a longitudinal cartridge detachably mounted thereto. The first jaw and the second jaw are connected to one another to permit movement in a substantially parallel relation between an open position, which permits capture of selected tissue between the jaws and an approximated position wherein the jaws are in close proximity to and in opposed alignment with each other. A knife assembly is provided having a bearing surface, a knife blade defining a cutting edge, and a latch receiver. The longitudinal cartridge slidably receives the knife assembly such that the cutting edge of the knife blade is permitted to move longitudinally between the jaws when the jaws are in the approximated position. A knife actuating mechanism having a bearing surface and a latch is provided for moving the knife assembly from a first position at a proximal end of the cartridge to a second position located distally from the proximal end of the cartridge when the knife actuating mechanism is moved distally. The latch is received in the latch receiver of the knife assembly for moving the knife assembly back from the second position to the first position when the knife actuating mechanism is moved proximally. A further mechanism is provided for disengaging the latch when the knife actuating mechanism moves between a latched position and an unlatched position.
An advantage of the detachable knife is that the knife actuating mechanism may now be a component separate from the cartridge holding the knife assembly. In stapling instrumentation, in particular, this means that a firing mechanism for the staples no longer needs to be an integral part of the disposable staple cartridge. Because of this, the cartridge may be made smaller. This reduction in size is particularly beneficial for surgical instrumentation used in endoscopic and laparoscopic procedures.
Other features and advantages of the present invention will become apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principals of the invention.